The present invention relates to micromotors, and more particularly relates to the fabrication of features on micromotor rotors wherein the rotors serve as prime movers.
Applicants"" copending application, cited above, reviews various work in the field of micromotor design and fabrication, and discloses a number of important improvements thereto.
The present application is directed to further improvements in micromachine technology, particularly to the design and fabrication of micromotors wherein the rotors are provided with working features (i.e. mirrors, gratings, fins, pump impellers, optical shutters, etc.) that are driven by the micromotor.
The present application is illustrated with reference to a particular application, namely the provision of mirrors on a micromotor rotor so as to enable micromachined optical scanning. While this is one important application of the disclosed technology, it should be recognized that the invention is not so limited. Instead, the invention finds application whenever the rotor of a micromotor is to be used as a prime mover in a system. (By prime mover, applicants mean that the rotor directly moves an element that performs the ultimate work of a given assembly. This is in contrast to use of a rotor simply to actuate a further assembly (as by intermeshed gears) wherein an element in that further assembly serves as the prime mover.)
In accordance with one embodiment of the present invention, a micromotor is fabricated using the same general process detailed in U.S. Pat. No. 5,705,318. However, before the rotor release step, a thick layer of photoresist is applied and exposed to define areas on the rotor where metal features (e.g. nickel mirrors) are to be attached. The substrate is then developed to remove the photoresist from the defined areas, leaving mold cavities. Electroless-plating is performed, filling the mold cavities with metal. The molding photoresist is thereafter removed, leaving metal plate structures extending from the rotor.
More generally, micromotors according to the present invention are fabricated with utilitarian features on their rotors. In some embodiments, the features are formed by the molded addition of material on top of a rotor surface. In other embodiments, the features are formed by the provision of an additional layer on top of the rotor, and the selective removal of material therefrom. In yet other embodiments, the features are defined by the selective removal of material from the rotor itself.
While illustrated with reference to polysilicon surface micromachined electrostatic motors, the invention finds applicability to all manner of micromachinery, including electromagnetic devices, and devices based on other structural materials and fabrication technologies.
The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.